The present invention generally relates to the focusing of laser light emitted by a laser transmitter and, in particular, to automatic focusing of laser light emitted by a laser transmitter.
Laser systems have been employed in numerous surveying and construction applications. In one such system, a laser light transmitting device provides a rotating laser beam which establishes a reference plane. Typically, the rotating laser beam is used to define, in effect, a continuous plane of light as a constant horizontal bench mark of elevation over an entire work area. The laser light is either detected by the naked eye or by one or more laser beam detectors, placed at considerable distances from the transmitting device. Various construction tasks can be performed based on the visual perception of the laser light. The detectors are used to intercept the rotating laser beam and determine an elevation at selected points throughout the work area. Such detectors may provide a display of the beam height for an operator or, alternatively, may form part of a machine control system that controls or assists in the control of various pieces of equipment, such as for example bulldozers and motorgraders.
In the laser light transmitting device, the generally horizontal plane of light is produced by projecting the beam upward and then deflecting the beam ninety degrees within a pentaprism or penta-mirror assembly. The pentaprism assembly is rotated about a generally vertical axis within the transmitting device to cause the horizontal beam to sweep around the axis and define the horizontal plane.
A focused beam of light, that is, a beam of light having a relatively small diameter at the working distance, increases the intensity of the beam per unit area, making the laser light more readily visible to the naked eye. The required focus is dependent on the distance between the laser light transmitting device and the desired focusing location, that is, the operating distance. A focusing lens may be used to focus the light emitted by the laser light transmitting device. Manual adjustment of the focusing lens has been used in the prior art. However, manual focusing requires that one operator adjust the focusing lens at or near the transmitter while a second individual reports the effect of such adjustment on the size of the beam, some distance away. The proper focus is therefore approximated by visual perception of an individual. Manual focusing is imprecise and time consuming, especially if performed by a single user who must continually leave the work area and readjust the focus as the desired focusing location changes. It will be appreciated that manual focusing over significant distances is quite difficult.
Accordingly, there is a need for an improved focusing system for a laser transmitter, and for an improved method by which such a focusing system operates.